Choosing the right sized backpack depends on three main factors
1. Length of Trip
2. Season
3. Backpacking Group
4. Type of Backpacker
1. Length of Trip
Most of the time the size backpack you choose will depend on the length of the trip you plan to take. The following are general recommendations based on length of trip
Day Hike (1 day) – 10 liters (610 cu/in)
Overnight Trip (2 days) – 35 liters (2,100 cu/in)
Multiday Trip (3-4 days) – 55 liters (3,400 cu/in)
Extended trip (5+ days) – 65 liters (4,000 cu/in)
2. Season
If you plan on traveling in colder weather then you are going to need an extra pack. While cold weather gear varies in size, I would easily add 10 liters to any of the recommended above sizes
3. Backpacking Group
Depending on the kind of group you backpack with you may need to carry more or less gear. For example, if you will be backpacking solo a larger pack will be required since you will have to carry all gear you would normally share with a partner. The same could be said for those traveling with family or small children.
4. Type of Backpacker
Some people pride themselves in their ability to minimize weight while others require a certain level of comfort even outdoors. The recommended sizes above are indented for lightweight backpackers. However, those willing to spend more money and forgo some comforts can easily fit all their gear in a backpacker 10 liters smaller than the recommended sizes.
